Integration of MR and Linear Accelerators (LINAC) opens new horizons in Radiotherapy by improved lesion targeting, especially for moving organs. In a practical implementation proposal, the LINAC rotates around the subject to hit the gross target volume (GTV) and clinical target volume (CTV) from multiple angles while minimizing the radiation exposure for surrounding tissues.
The combination of magnetic resonance apparatuses and LINAC radiotherapy sources is known. Typically a LINAC source is placed on a rotating gantry about the magnet and the magnet designed such that the LINAC rotates in a zero-field region of the magnet. Another particular feature of the concept is the use of a split gradient coil which prevents attenuation of the LINAC beam.
In brachytherapy, a catheter is inserted into a subject. Then a radioactive source is controllably inserted into the catheter to irradiate the subject. In brachytherapy systems (e.g. for high dose rate brachytherapy) the radioactive source can be withdrawn from the catheter after a predetermined amount of time.
United Stated Patent application US 2011/0160566 discloses the guiding of electron beam or X-ray beam therapy and brachytherapy using a magnetic resonance imaging system by registering ultrasound images to a previously acquired magnetic resonance image.